1. Field of the Invention
This invention relates to an improved shaftless radial vane rotary device such as a fluid motor, fluid pump, compressor or the like, and to an improved marine propulsion system using the device as a drive motor. The propulsion system includes a propeller having its blade tips rigidly joined to the inner periphery of an open-center tubular rotor of the device, with the stator being adapted to be joined to and supported on the hull of a marine vessel.
2. Description of the Prior Art
Radial vane rotary devices such as motors, pumps and compressors are known in which a plurality of equally spaced vanes are mounted in radial slots in a cylindrical rotor body and are biased outwardly from the rotor into contact with the inner surface of a stator. Various configuration of the rotor and stator are known; for example, a cylindrical rotor may be mounted with its axis offset relative to the central axis of the stator, or the rotor and stator may be coaxial, with the stator having a contoured surface cooperating with the movable vanes to provide expanding and contracting chambers upon rotation of the rotor. For example, the stator surface may be or oval an elliptical shape or may have a number of lobes around its inner surface.
The vane-supporting slots of the known device have been difficult and expensive to produce in that they have generally been machined into a relatively large body of rigid material, usually metal, and smooth surfaces are necessary to minimize friction with the sliding vanes. Also, the grooves have to be accurately dimensional to control the flow of fluid along the surfaces of the vanes in the grooves. To assure continuous contact while avoiding excessive pressure between the vane edges and the stator surface, it is known to vent the bottoms of the grooves.
U.S. Pat. No. 6,106,255 discloses a radial vane rotary motor in which the vanes are supported in radial slots in a rotor body supported on a shaft for rotation in a rotor chamber defined by a cylindrical stator body having its ends closed by end plates. Grooves in the end plates are provided to facilitate venting of trapped fluid from beneath the movable vanes. This patent also discloses the use of grooves in the vanes for relieving excess pressure from beneath the slots.
U.S. Pat. No. 6,629,829 also discloses a radial vane rotary motor including vents through spring biased end plates to vent the vane supporting grooves. The vents communicate with a pressurized fluid chamber in the stator body.
Various systems have also been developed in a attempt to improve propeller performance and propeller drive efficiency in marine vessel propulsion. The shrouded rudder in which the propeller is driven inside a fixed or pivotable shroud, such as the well-known Kort rudder, is one example.
It is also known to rigidly join the propeller blade tips to the inside surface of a peripheral rim in spoke-like fashion, with the rim being driven for rotation to apply the driving force to the propeller. U.S. Pat. No. 472,199 discloses such an arrangement in which the outer periphery of the rim is provided with vanes, or buckets, with nozzles directing streams of pressurized water into the vanes to drive the propeller in waterwheel fashion.
U.S. Pat. No. 3,487,805 discloses a propulsion system in which a propeller-supporting rim is mounted for rotation in a nozzle by a water-lubricated rubber bearing and is driven by a gear mechanism including a drive gear extending around the periphery or the rim. The rim-supported propeller rotates about a fixed axis, and a blade rudder is positioned behind the propeller for steering.
U.S. Pat. No. 5,722,864 discloses a rim-mounted propeller in which the rim is the rotor of a tubular hydraulic motor. Sleeve bearings are used to rotatably support the rotor in the stator, but no bearing arrangement is disclosed for transferring the propeller thrust to the stator and from the stator support struts to the vessel. Rubber seals are employed to keep water out of the motor. Movable vanes are employed on the rotor, with camming means on the stator depressing the vanes between the inlet and exhaust ports.
U.S. Pat. No. 4,831,297 discloses a propeller drive system in which the propeller blade tips are mounted on the inner periphery of a tubular rotor disposed inside the stator of an electric motor. Hubs at each end of the stator have spoke-like members attached to and supporting the rotor, and a flange is provided on one hub for rigidly mounting the structure to a vessel. This rotor and propeller are rotatably supported by a cylindrical, or journal bearing on a shaft extending between the two stator hubs.
U.S. Pat. No. 5,967,749 discloses a marine vessel propulsion system in which a variable pitch propeller has the inner ends of its blades pivotably supported on a shaft-mounted hub and its outer ends joined by pins to first and second surrounding rings. Permanent magnets are mounted on one of the rings, and coils on the other ring may be supplied with current to rotate the rings relative to one another to vary the pitch. As with the other patents mentioned above, a separate rudder system would be required for steering the vessel.
While the rimmed propellers of the prior art, discussed above, would appear to be efficient in converting the propeller drive force to thrust, these devices have not met with wide-spread acceptance for various reasons. For example, all would appear to present severe maintenance problems, particularly in the use of sleeve bearings or the like for transmitting thrust, as well as in providing adequate lubrication of movable parts. The prior art sealing arrangements, particularly for electrically driven systems, present serious problems. Further, the known rim mounted propellers generally require separate rudder systems for steering, and generally have not been energy efficient. Accordingly, it is a primary object of the present invention to provide a hydraulic motor driven rimmed propeller system which overcomes the shortcomings of the prior art systems.
Another object is to provide such a system suitable for use both as a primary propulsion system and as a side thruster for vessels.
Another object is to provide a rim mounted propeller system driven by a hydraulic motor, utilizing the rim as a rotor, which is economical both to manufacture and to maintain.
Another object is to provide such a system in which the rotor is mounted in the stator utilizing ball bearing assemblies on each end which are capable of carrying both radial and axial thrust loads and which are lubricated by the hydraulic fluid used to drive the motor.
Another object is to provide such a system which utilizes a standard spring loaded, self-adjusting marine packing gland as a water/oil seal, thereby avoiding the use of custom-made rubber seals.
Another object is to provide such a system utilizing a hydraulic motor having movable, spring loaded vanes which have pressure ports assisting the springs in maintaining the movable portion of the vanes in contact with the stator inner surface, and pressure relief ports which assist in lubricating the face of the vane which contacts the stator surface.
Another object is to provide such a system including a pivotal mounting structure rigidly joined to the stator for supporting the motor for rotation about its vertical axis, thereby eliminating the need for a separate steering rudder for the vessel.
Another object is to provide such a system in which the major components of the hydraulic motor are constructed from standard structural shapes to thereby reduce manufacturing costs.
Another objection is to provide an improved radial vane rotary device having spring-loaded vanes supported for substantially radial movement on the rotor, which vanes have pressure ports and/or shuttle valves for assisting the springs in maintaining the vanes in contact with stator surface while assuring freedom of movement of the vanes during rotation of the rotor.
Another object is to provide such a device which is economical to manufacture and easy to maintain.
Another object is to provide such a device in which the radial vanes are mounted in guides attached to the outer cylindrical surface of a rotor body mounted within the stator.